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How To Develop Java Using Textpad

By Ernest Lopez,2014-04-24 12:11
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How To Develop Java Using Textpad

    How To Develop Java Using Textpad

The TextPad text editor that came on your student CD has many features that will help

    you write Java source code. The trick is to let TextPad know you are writing Java and not

    something else.

As an experiment, open one of the .java files that came with your student files in TextPad.

    Note that the text is color coded. Keywords are blue, punctuation symbols are red,

    comments are green, and literals (literal strings enclosed in “”, for example) are a sort of

    turquoise. The color coding is designed to help you recognize and correct mistakes more

    easily.

Now, as a second experiment, open a new document in TextPad and start writing a

    simple Java application. Use the three lines below if you wish:

// A simple Java program

    Public class MyFirst

    {

Notice that the text you typed is not color coded as was the program you opened. That’s

    because TextPad does not know you’re writing Java (yet). To tell TextPad you’re a Java

    programmer, save your file using the extension .java. Use Save As from the file menu to

    name your file correctly and place it in the directory of your choice. A good habit to

    develop is to write the first line or two of a new program, then save it using the correct

    class name with .java extension, then continue writing your code.

***Note*** You must name the file using the name of the declared public class!!

    If you do not, Java will refuse to compile your code.

In the example above, the name of the file must be: MyFirst.java

    Java is a case-sensitive language. The file name must be identical to the class name in

    both spelling and case. In other words, myfirst.java is incorrect and will not work.

Note that once you save the file with a .java extension, TextPad displays your code with

    the color coding described earlier.

Look at the options available in the TextPad Tools menu. Note the last three:

    Compile Java

    Run Java Application

    Run Java Applet

These commands allow you to quickly and easily compile and execute your Java

    programs without using a command prompt window or memorizing commands.

    To compile your Java source code, simply select Compile Java from the Tools menu.

    If your code is free of syntax errors, your source code will reappear in the edit window

    and a message: “Tool completed successfully” will be displayed in the Status Bar

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(bottom-left of the TextPad window). If errors are found, an error list will be displayed in

    the edit window. The error messages are reasonably clear and include a line number in

    the source code where the error was encountered. At this point, you may want to have

    TextPad display line numbers with your source code. Select the View menu, then the Line Numbers selection. TextPad will now display line numbers with your code. (Note:

    the line numbers do not become part of your code saved to your file).

To return from the error list displayed in the edit window, to your source code, simply

    select your source code file from the list of open files displayed in the window just to the

    left of your edit window. If you selected View->line Numbers, you will see line numbers

    displayed with your code.

    **A word on correcting syntax errors** Always fix the first (topmost) error in the list! Then, recompile your source code. Why? Because the compiler can become “confused”

    as errors are encountered and will begin to list errors that are not really there. Fixing the

    first error will often remove several subsequent errors from the list because the compiler

    now “understands” what you were trying to do. Continue this process until all syntax

    errors are eliminated.

Once you have compiled your source code successfully (no errors), you can run your

    Java application (applets will be discussed at the appropriate time as the class progresses)

    by selecting Tools-> Run Java Application in TextPad. Your application will run an display output in a command prompt window.

    The following applies to CIT1613 students only. Getting user input into your Java programs: Although this topic has nothing to do with TextPad, per se, I’m including it here because you’ll encounter the need to capture

    user input almost immediately. The author presents two alternative ways to capture user

    input from the keyboard.

    1. Use the Scanner class as instructed in your book.

    2. Use JOptionPane dialogs to display prompts and capture input. If you use this

    option, you must use an import statement to let Java know where to find the

    desired class in the Java API. The statement you need to add, before your public

    class header, is (with a comment included):

    //import javax.swing.JOptionPane;

    import javax.swing.*;

This should get you started. Have fun with Java!

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